The long-term objective of the project is to characterize at the molecular level: (a) the transduction of signals between the cardiotropic agent Trypanosoma cruzi and host myocardial cells (synthesis and mobilization of second messengers); (b) the molecular structure of complementary T. cruzi attachment molecules of myocardial cell surface receptors (beta adrenergic and muscarinic receptors); (c) the cDNA of complementary T. cruzi attachment epitopes; (d) immunogenicity of complementary T. cruzi attachment epitopes, and, (e) the degree of protection from parasitosis in nonprimates and non-human primates provoked by immunization with T. cruzi attachment epitope look-alikes. Chronic Chagas myocarditis is the quintessential human example of postinfectious myocarditis, a process believed to result from immunopathogenic mechanisms and in cardiomyopathy and progressive congestive heart failure. The experimental design takes advantage of recently obtained knowledge of the kinetics of recognition and adhesion of T. cruzi plasma membrane vesicles (PMVs) to surface receptors of the striated muscle membrane. Assay of second messenger formation and mobilization (cAMP; IP3; DAG and Ca2+) will be made to establish coupling of the recognition and adhesion process. Complementary T. cruzi attachment molecules (cTAMs) will be solubilized with detergents and purified by affinity immunoabsorbents and by HPLC techniques and the amino acid sequence measured. A Xgtll cDNA library of T. cruzi metacyclic trypomastigotes will be surveyed from constructed oligonucleotides and attachment epitopes identified in recombinant cells. The immunology of T. cruzi attachment epitopes will be characterized to determine pathogenicity to myocardial cells by study of myocarditis development and possible coupling to levels of antimyocardial cell anti-Id antibodies and to cytotoxicity of T cells in immunized syngeneic inbred mice. Immunoprotection from T. cruzi infection provoked by attachment molecule epitope immunization will be measured using LD50 innoculations providing critical data for vaccine design.